In electronics, “load regulation” is concerned with the capability to maintain a constant voltage (or current) level on the output channel of a power supply despite changes in load. A voltage regulator is a switching power supply that supplies a steady voltage to a load. A voltage regulator that supplies voltage to a Central Processing Unit (CPU) is a CPU voltage regulator, CPU voltage regulators receive one voltage and supply a second voltage to a processor (in this case the processor is a CPU which is sometimes also known as a microprocessor).
When the load current suddenly increases, such as when the processor state changes from idle to active, the voltage supplied to the processor is drawn down, known as a voltage transient or voltage droop 16 (see FIG. 1). Likewise, a voltage spike may occur when the processor state changes from active to idle. Changes in state may also result in voltage overshoot 18. Overshoots 18 describe the fact that a transient voltage value does not stop precisely at its destination voltage, but rather shoots past (i.e. over) the destination voltage and then reverses back. Additional overshoots are often experienced, with each successive overshoot having a smaller magnitude than the previous. The voltages supplied at active and idle processor states are further provided at levels that ensure that such droops, spikes, and overshoots will not take the voltage level outside of necessary limits.
Accordingly, during times of low current, more voltage is supplied than is necessary for the experienced load. In designing the circuit and setting the voltage to be supplied, designers must determine a “worst case” voltage transient that could result from one or more inactive (idle) blocks becoming active. The voltage supplied must be high enough to handle the worst case transient. The difference between this supplied voltage and the voltage necessary to power the currently active blocks (the load) is a protection voltage. This protection voltage results in increased power consumption in the low current state relative to what is necessary for the experienced load. Increased power consumption results in increased power costs and produces increased heat. Additionally the extra heat produced contributes to an overall heat produced by the circuit. When the heat produced by a circuit is at or above the amount of heat that the circuit can dispose of, the operations of the circuit must be altered, for example, by reducing clock speed, making blocks inactive, or otherwise reducing the amount of heat being produced. Accordingly, the artificially inflated load voltage leads to reduced processing speed of the circuit. Additionally, artificially inflated load voltage leads to increased current and power use. Such increased current and power use can reduce battery life for devices operating off of a battery.
Accordingly, there exists a need for an improved method and apparatus that provides regulation while reducing any excess heat and performance drain beyond that necessary to power the attached load. Furthermore, there exists a need to supply the needed power without placing the circuit at risk for damage from voltage droop and overshoot.